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That's not an easy question. IF she can get in, IF they let her in, then yes, she can apply for Lawful Permanent Resident status without having to leave the U.S. But the problme is that she is not supposed to use a B-2 tourist visa to enter the U.S. if her intention is to stay which it basically would be. So I think that they pretty much will not let her in. The only exception that exists is for immediate relatives of U.S. Citizens. Here is a link:
So honestly, I would not even try. The chances of her getting in are slim and the chances are high of her being denied entry and given a 5 year exclusion penalty or permanent penalty which means that she would have to apply for a waiver to come back. The risk of the 5 year or permanent penalty is if she tries to lie to them about her intention. So again, I would not risk this. I am truly sorry. I know it is inconvenient, I know you want to be together quicker than later, but I would play it safe.
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